It's where the micro-rotor movement really scores over a traditional automatic, not obscuring 50%+ of the movement with a great big rotor. I had to smile at some of the annoyance people were expressing when the TAG-Heuer Carreras went with the Fangio caseback on some models, rather than the sapphire one - as if the Vj7750 was some beautiful movement and they were missing out on seeing that. It's hardly that, it's a big rotor and recent ones even have a further plate covering most of the rest of the mechanicals - hardly anything worth seeing on it! Just like modern engines with their plastic shrouds:

Hardly something to get the heart pumping, is it? Not like:

Quite why the fashion for see-through casebacks came along when most movements are no longer worth looking at is another puzzle to me :s